Improving Fracture Resistance of 5Y-PSZ-based Three-unit Bridge Prosthesis.

5Y-PSZ-based zirconia dental restorations exhibit high translucency and good esthetics but have a higher fracture risk compared to 3Y-TZP. To investigate the effect of BruxZir SteelTM treatment on the fracture resistance of zirconia three-unit bridges prepared using 5Y-PSZ-based zirconia blanks. Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Their fracture resistance was analyzed by dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir SteelTM) was compared with the sintered control restoration (untreated cementation surface). Finite Element Analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load. The fracture resistance of the test restorations was significantly higher than that of the control restorations for all the manufacturers considered in this study (P < 0.05). Furthermore, the restoration made of BruxZirⓇ Esthetic treated with BruxZir SteelTM had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blocks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir SteelTM treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of BruxZir Steel-treated sample compared to the control. The fracture resistance of 5Y-PSZ-based BruxZir SteelTM-treated three-unit bridges was significantly higher (min. 30%, max. 198%) than control.